Just to be sure: are you able to use the right transformer secondaries for the loudspeaker impedance? Between a 4 and a 16 ohms tap is a 6dB difference in output voltage level (3dB between 4-8 or 8-16).

Hi Coen, I sent Reinhard Thöress (designer/manufacturer of my amps) the specs of my horns, and he recommended going for the 4 Ohm taps. I think he felt 109dB/W was plenty to be playing with, but perhaps I should have made it clear that the NOS1 output is slightly less than most other DACs. The taps are hard-wired inside the amps, though can be changed. So it's good to know that if I really need more gain, I could change to the 8 or 16 Ohm taps.

Hi Coen, I sent Reinhard Thöress (designer/manufacturer of my amps) the specs of my horns, and he recommended going for the 4 Ohm taps. I think he felt 109dB/W was plenty to be playing with, but perhaps I should have made it clear that the NOS1 output is slightly less than most other DACs. The taps are hard-wired inside the amps, though can be changed. So it's good to know that if I really need more gain, I could change to the 8 or 16 Ohm taps.

Thanks for pointing this out.

Mani.

Hi Mani,

You should definitely go for better matching of transformer and speaker. I had to insert Pault Spelz "Zeroformers" to get sufficient power for my 100dB+ 16 ohm baffles. These are quite versatile so I experimented a bit and learned that 6dB is a LOT of extra output especially since my "power" amp is so feeble in the first place (5ohm output tap). I was able to optimize the sound quality by finding the best coupling.

These "Thöress" amps are very nice looking retro styled amps. I am pleased to hear they sound good too. Wich one do you have the 300B or 845? Their low sensitivity is part of the design philosophy so a preamp (that actually amplifies) is actually expected.

I'd have to sort ou how much more is possible, but in theory the 6dB is achievable.

Best regards,Peter

OK, that was too much of theory. Sadly, it is 1dB only and I wouldn't even do that;A tiny bit more and it goes wrong. No not even headroom above that 1dB - the 1dB *is* the headroom. Not advised now I know it anyway ...

With only 1dB of headroom, would you recommend not playing back at 0dB attenuation in XX?

From the top of my head, I can think of only a handful of 24 bit (mostly classical) albums that I have that I'd ideally like to play back with more volume than 0dB currently gives me. So this really isn't much of an issue at all... but would have been nice.

With only 1dB of headroom, would you recommend not playing back at 0dB attenuation in XX?

Mani, what slipped through my mind after seeing the results yesterday, is dat you had a remark which was related IIRC, about your two NOS1a's both behaving drifferently regarding 0dBFS. Am I right ? now, it can be just this ...

I wanted to ask you anyway what this was about, because we now have yours both here ...

I was going to mention this, but thought it might just complicate things.

Yes, it seemed to me that the sound changed between XX set to 0dB and any other volume setting. 0dB sounded 'thicker', with a loss of sparkle in the sound. And my feeling was that this had nothing to do with clipping or headroom, because the material I was using had an RMS level of -20dB or so. I also felt that it was an 'issue' with XX and not the NOS1 (either of them).

In any event, this is no longer relevant in my office system because I have removed the preamp and tend to playback on XX/HQP at around -30dB. But in my main system, I'm tending to playback on XX at between -6dB and -1.5dB. I avoid playing back at 0dB for the reason cited above (even if the RMS level of the material is low).

Sure. It is only that the RMS level doesn't tell much (but depending how you audibly observe). Thus, with e.g. a drumming track the RMS level will be very low, while each hit can reach maximum digital level.

When you'd normalise the volume of an album of concern (via XXHighEnd), you can look in the XXAnalysis.dat file which resides in the folder where the track files are to see the max level - 32767 is maximum. 6dB less is half of that (3dB is 25% less).

When you'd normalise the volume of an album of concern (via XXHighEnd), you can look in the XXAnalysis.dat file which resides in the folder where the track files are to see the max level - 32767 is maximum. 6dB less is half of that (3dB is 25% less.

I've been using TT DR Meter to check RMS and peak levels, but I'll use XX too from now on. Actually, looking at a drum kit track, I can see exactly what you mean.